import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution5 {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode deleteDuplicates (ListNode head) {
        // write code here
        ListNode cur = head;
        while(cur != null) {
            int val = cur.val;
            ListNode c = cur.next;
            while(c != null && val == c.val) {
                c = c.next;
            }
            cur.next = c;
            cur = cur.next;
        }
        return head;
    }
}